Klinefelter's Syndrome / XXY Males: The Effects of Having an Extra Chromosome in Males

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Klinefelter’s syndrome, (also known as 47,XXY or XXY syndrome) is a genetic disorder in males caused by having an extra X chromosome instead of the usual XY pattern that men have. Klinefelter’s syndrome is one of the most common chromosome abnormalities in humans since it has been estimated that 1 in 500 boys have it. The severity of the condition is variable. The main issue with Klinefelter’s syndrome is male infertility but a variety of other symptoms may occur including problems with physical, language, and social development.

What causes Klinefelter’s syndrome?

Klinefelter’s syndrome is a genetic disorder caused by a process known as “chromosome aneuploidy.” Every cell in the human body has 23 pairs of chromosomes (for a total of 46). The 23rd pair of chromosomes are the sex chromosomes. Females typically have two X chromosomes, while males typically have one X chromosome and one Y chromosome.

Sometimes during cell division a non-correct disjunction of chromosomes may occur. This is where chromosomes fail to separate properly during meiosis, and in this case results in an extra copy of an X chromosome. When a gamete of this type is fertilised by a normal gamete, there will be an unequal number of chromosomes in all the resulting cells of the new individual.

Symptoms of the XXY condition

In general, there is a delay in physical development in males who have the genetic abnormality. Normal physical milestones such as sitting, crawling, and walking are achieved at older ages in Klinefelter’s patients. Weak muscles and reduced strength are usually observed in babies and toddlers with the syndrome. They tend to be taller with less muscular development, less hair on face and body, and broader hips. Also they usually have less energy than regular boys. In adulthood, XXY males are taller and tend to develop health issues such as autoimmune disorders, breast cancer, vein diseases, osteoporosis, and tooth decay. Male infertility is the most common issue in males with Klinefelter’s disease.

XXY males usually have language problems. They learn to speak late and have problems using language to express thoughts. Also, Klinefelter’s males have a harder time at reading and writing assignments.

Klinefelter’s babies and teens tend to be quiet and shy. They have trouble keeping up with others at school and sports and usually have problems fitting within the group because of their lack of self-confidence. As adults, and with proper treatment, Klinefelter’s patients can live a normal life with friends, families, and develop normal social relationships.


Unfortunately Klinefelter’s is irreversible. However, once diagnosed, Klinefelter’s patients have a variety of things they can do to manage the disease appropriately. The important thing is to start as soon as possible and early in the patient’s life.

Physical, language, occupational, behavioral, and family therapies are utilized to treat and manage the symptoms of Klinefelter’s syndrome. Testosterone replacement therapy (TRT) may help XXY males balance their testosterone levels. Normal testosterone levels may help XXY patients develop bigger muscles, deepen the voice, and grow facial and body hair. And fertility treatments can help them to become parents.


Klinefelter’s Syndrome